Solar cells are actively developed to deal with current environmental issues and energy issues, and various kinds of materials including from conventional single crystal silicon to thin film silicon, organic compound, and dye sensitization have been developed. In addition, various structures including from a conventional single junction to a lamination type multi junction have been developed.
In view of the above situation, methods of fairly evaluating photoelectric conversion efficiencies of those solar cells are provided in the internationally standardized methods of evaluation, IEC60904 and JIS (C8905-C8991). Those provisions are summarized as follows: generated electric power of a solar cell is measured under illumination of an illumination device (herein after, referred to as solar simulator) that irradiates light simulated to have the same spectroscopic spectrum and irradiance as the standard sunlight.
Here, the standard sunlight represents sunlight with AM 1.5, which is sunlight obliquely entering the earth's surface through 1.5 times optical path length of AM 1.0, where the sunlight of Air Mass (hereinafter, referred to as AM) 1.0 is defined as the sunlight perpendicularly entering the earth's surface. Generally, it is the light from the sun having an elevation angle of 41.8 degrees relative to the earth's surface, and the sunlight from the bright and clear sky in spring or autumn in Japan is relatively close to the standard sunlight.
However, it is difficult for individual inspection agencies and business entities to have and operate solar simulators having the same spectroscopic spectrum and irradiance as the standard sunlight. For this reason, as a practical way, a standard solar cell having the same relative spectral sensitivity characteristics as a solar cell is made and calibrated by using a highly-simulated solar simulator having characteristics ultimately similar to a standard sunlight owned by public institutions (for example, the National Institute of Advanced Industrial Science and Technology in Japan). The individual inspection agencies and business entities adjust the light amount of their own solar simulator by using the calibrated standard solar cell and then measure a solar cell.
For example, in Non-Patent Document 1, a short-circuit current value of the solar cell similar to an object to be measured is measured under the illumination condition having a spectral irradiance similar to that of the standard sunlight, and the solar cell is made to be a standard solar cell being assigned a short-circuit current value whose spectrum-nonsimilarity error has been corrected. The following method is provided such that: the standard solar cell having been assigned the short-circuit current value is placed under the solar simulator; and the light amount of the solar simulator is adjusted so that the short-circuit current value of the standard solar cell is equal to the short-circuit current value; then the characteristics of the solar cell to be measured is evaluated.